Headlamp for automobiles



Oct. 28 1924.

W. E. MARSHALL ET AL HEADLAMP FOR AUTOMOBILES Filed March 2O 1924atented Oct. 428, 1924.

WILLIAM EDWARD HLL AND PHILIP GEORGE P-AGE MCCULLOCH, OFLONDO-N,ENGLAND, ASSIGNOBS T0 NON-DAZLITE, LIMITED, OF LONDON, ENGLAND.

HEADLAMP FOB AUTOMOBILES.

Application led Marcho 20, 1924. Serial No. 700,541.

l To all whom t may concern.

Be it known that we, WILLIAM EDWARD MARSHALL and PHILIP GEORGE PAGEMGCUL- LocII, both subjects of the King of Great Britain, residing at 32Mortimer Street. London, England, have invented new and usefulImprovements in Headlamps for Automobiles, of which the following is aspecification. l

This invention relates to improvements in head lamps suitable forautomobiles.

The object of this invention is to provide a head lam in which the beamtherefrom whilst sufficlently illuminating the road will not dazzlepersons facing the lam We have found that with head lamps having aparaboloidal reflector, the focal length of which is an inch and aquarter or less (this being the focal length of reflectors at presentcommonly used), the rays reflected from the central portion of thereflector-have a divergence at least four or five times greater thanthat of those proceeding from the outer portions thereof, thisdivergence being due to the great dierence between the maximum andminimum distances of the filament from the refiector.

We have also found that a reflector having a focal length of two inchesreduces the maximum divergence of the rays from thel central portion ofthe reflector to less than twice that of the rays reflected from theouter portions.

In a head lamp constructed according to our invention the reflector hasa focal length of at least two inches and preferably three inches ormore, and in order toobtain a beam of light, the vertical section ofwhich is considerably smaller than the horizontal section, so as toilluminate the sides of the road whilst at the same time keeping the topof the beam below the level of the eyes of an approaching pedestrian, weemploy an incandescent electric lamp the filament of which is arrangedhorizontally in a plane at right angles to the axis of the reector, thebulb of the electric lamp being preferably spherical and the filamentconsisting referposition on the head lamp) this distance preferablybeing less than two millimetres and in no case greatly exceeding it, theob- ]ect being to ensure that the whole of the filament is'slightly infront of the centre of curvature of the bulb.

The coil may be of considerable length, for example, three quarters ofan inch or more.

With an electric lamp so constructed, the comparatively large4percentage of rays reflected back from the glass of the bulb itself onto the refiector are divergent to a slight extent only, and only thoseproceeding from the upper portion of the reflector therefore riseupwards from the horizontal.

The electric lamp may be supported in an externally screw threadedholder, screwing into a threaded hole in the body of the lamp and heldin position by an external lock nut, the holder being of such lengththat the centre of the filament can be placed in the focus of thereflector,'that is, outside the plane of the ed e of the reflector.

In t e accompanying drawings which illustrate the invention, Figure 1 isa vertical section with parts in elevation of a head lamp embodying theinvention; Figure 2 is a plan view of the bulb and filament; and Figure3 is a side elevation of the bulb and filament of Figure 2.

1 is the lamp body, 2 a paraboloidal reflector having a focal length ofthree inches.

3 is a spring ring for keeping the reflector in I position; 4 is anelectric lam holder having an externally screw threade portion 5, and 6is a tapped socket in which the screw threaded portion 5 of the lampholder engages; 7 is a lock nut retaining the holder 4 in position aftercorrect adjustment. 8 is an electric lamp having a spherical bulb'(except for the pip). A--A is a line passing through the geometricalcentre of the bulb. 9 is the filament coil situated in front thereof ata distance of 2 mm. therefrom, so that the whole of the filament isslightly in front of the line A-LA,

The arrangement shown provides means which allow existing lamp casingbodies to be readily fitted with a reflector of greater focal length. l

The use of a two inch reflector will reduce the maximum divergence ofthe rays vfrom the central portion of the reector to less than twicethatof the rays reflected from the outer portions, and with the use oita redector of still greater local length, this reduction is markedlylarger.

Moreover, when employing an electric lamp as shown in Figures 2 and 3, abeam of* light is produced having a lateral spread as large as isrequired, but in which the upward divergence is almost or entirelyeliminated, such upward divergence beingone of the main causes of thedazzling edect in lamps as heretofore used.

What we claim is A vehicle headlight comprising a casing, asubstantially paraboloidal redectr within 7 the casing, the focal lengthof which is greater than two inches, a socket supported axially of thereflector, and a light source in the socket lying at the locus of thereflector, outside the plane oit the edge thereof and within theboundary of the casing, said light source comprising a substantiallyspherical incandescent lamp bulb having a long horizontal .lilamentlying` in front of the geometrical as our invention we have signed ournames 30 this 10th day of March, 1924.

WllllAlll EDWARD lvlAlRSllAll.. l Pl'lllllD GERGIE PAGE lvlcClIlilCll.

